The use of solar energy can replace significant amounts of fossil fuels, in order to decrease climate changing emissions. Thus, the ratio of the photovoltaic (PV) electricity in the energy mix has increased at an accelerated pace and this trend is expected to continue in the future. As PV panels are widely used, those installed for years now have to be monitored, and when their parameters reach critically low values, they have to be replaced [1, 2]. This issue of PVs, related to the change of the parameters over time is unavoidable due to their exposure to rough atmospheric conditions: solar radiation [3], thermal differences between day and night (as well as between seasons), wind, dust, and humidity. The aim of the present study is to propose for the assessment and monitoring of such structural changes a non-destructive method that can be used in situ: Optical Coherence Tomography (OCT) [4-6]. Other optical and mechanical methods are used to validate the experimental findings using OCT, including: optical and Scanning Electronic Microscopy (SEM) [7], as well as mechanical investigation methods such as roughness and hardness measurements. Two categories of samples are considered for the study: news PV cells and PV cells that have been exposed to various atmospheric conditions (the most significant ones being the temperature influence) for several years. The changes in their structure and properties are determined and discussed.